Reproducibility: Reliability and agreement of short version of Western Ontario Rotator Cuff Index (Short-WORC) in patients with rotator cuff disorders.

INTRODUCTION

Recently, a shorter version of Western Ontario Rotator Cuff Index (Short-WORC) was proposed as a subset of 7 items from the original 21-item WORC. However, the reproducibility of the Short-WORC has not been established.

PURPOSE OF THE STUDY: To determine reproducibility (reliability and agreement) of the Short-WORC among patients with rotator cuff disorders (RCDs).

METHODS

Patients (n = 153) diagnosed with RCD completed the WORC at baseline and at 3 months post-operatively (n = 146). The Short-WORC was extracted from the full version of WORC. From this retrospective cohort, 43 patients were retested within 5 weeks, if they remained stable. Cronbach's alpha (α) and intra class correlation coefficients (ICC2,1) were used to assess internal consistency and test-retest reliability respectively. Standard error measurement (SEM), minimal detectable change (MDC90) and Bland Altman (BA) plots were used to assess agreement.

RESULTS

No floor and ceiling effects were reported for either the Short-WORC or WORC. Cronbach's α were 0.84 and 0.90 at baseline and 0.89 and 0.95 at 3 month of follow up for Short-WORC and WORC respectively. The ICC2,1 were 0.89 and 0.91 for the Short-WORC and WORC respectively. The agreement parameters for the Short-WORC were: SEMagreement = 8.8, MDC90individual = 20.3, MDC90group = 5.1. We found substantial agreement between the two versions of WORC on BA plots with minimal (mean difference (d) <1) systematic differences between them. The limits of agreement (LOA) between two versions of WORC were similar across sessions and fell within range of -11.7 to 13.2 points at test and -14.7 to 14.7 points at retest.

CONCLUSION

Short-WORC and WORC demonstrates strong reproducibility and can be used for group and individual comparison of health-related quality of life (HRQoL) among patients with RCD. Wider LOA may be expected when using the Short-WORC for individual patient assessment. Reproducibility data is essential, but should be supplemented by validation of actual Short-WORC with samples representing the spectrum of RCD.

LEVEL OF EVIDENCE: N/A.